Allâh cursed him. And he [Shaitân (Satan)] said: "I will take an appointed portion of your slaves; (4:118)

Verily, I will mislead them, and surely, I will arouse in them false desires; and certainly, I will order them to slit the ears of cattle, and indeed I will order them to change the nature created by Allâh." And whoever takes Shaitân (Satan) as a Walî (protector or helper) instead of Allâh, has surely suffered a manifest loss. (4:119)

Now we can focus, what the Qur'an is mentioning about the people Allah has made so beautiful, and they are trying to copy the wild scary faces, and dresses which leads towards Shaytan (Satan).

Our beloved Prophet (SAW) said: "Who imitates any other nation must be one of them." (Abu Dawud)

These celebrations are against Islam. And functions like this only result in to crimes and sometimes when kids are given candy while trick or treating, the candy is found to be mixed with blades, and poison.

Beware, any action or function followed by the non Muslims, that means we are one of them.